In typical speech recognition, the rate of false recognition may increase due to a high level of background noise and the like. In order to avoid this problem, improved speech recognition techniques have been accomplished, such as one disclosed in Unexamined Japanese Patent Application Kokai Publication No. H11-161292. This technique uses a plurality of standard patterns for each segment of speech to be recognized. Input speech is evaluated with scores for the respective standard patterns and then recognized based on the scores. The scores are varied depending on the level of background noise. This speech recognition technique leads to a reduction in the rate of false recognition due to background noise.